Spinnerets and silk-producing system of Segestria senoculata (Araneae, Araneomorphae, Segestriidae)

The spinning apparatus and silk of Segestria senoculata were studied with the use of scanning electron microscopy and light microscopy, which confirmed the presence of four categories of spigots connected with four types of spinning glands (i.e., Glandulae ampullaceae major, Glandulae ampullaceae minor, Glandulae piriformes and Glandulae pseudaciniformes). New data about the morphology of spinnerets and spigots were obtained for both the adults and nymphal stages of both sexes. For the first time the silken threads of retreats, signal threads and attachment discs of the members of Segestria were subjected to a detailed SEM study. The data resulting from studying the spinning apparatus of S. senoculata was compared to current knowledge of the silk producing systems of families belonging to the Dysderoidea superfamily. Silks that are emitted from spigots in the course of retreat construction are not (similarly to the other dysderoids) processed by the spider’s legs during the subsequent process of hardening. Apart from the major ampullate glands/spigots, segestriids also possess developed minor ampullate glands. Minor ampullate threads are used by S. senoculata spiders when making their signal threads.